Purifying crude furan 2,5-dicarboxylic acid by hydrogenation

ABSTRACT

A process for purifying a crude furan 2,5-dicarboxylic acid composition (cFDCA) by hydrogenation of a FDCA composition dissolved in a hydrogenation solvent such as water, and hydrogenating under mild conditions, such as at a temperature within a range of 130° C. to 225° C. by contacting the solvated FDCA composition with hydrogen in the presence of a hydrogenation catalyst under a hydrogen partial pressure within a range of 10 psi to 900 psi. A product FDCA composition is produced having a low amount of tetrahydrofuran dicarboxylic acid, a low b*, and a low amount of 5-formyl furan-2-carboxylic acid (FFCA).

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of pending U.S. patent application Ser.No. 13/758,080, filed on 4 Feb. 2013, which claims the priority to U.S.Provisional Patent Application No. 61/663,246, filed on 22 Jun. 2012,and the entire disclosures of each are incorporated herein by reference.

FIELD OF THE INVENTION

This invention relates generally to the production of purified furan2,5-dicarboxylic acids. In particular, the invention relates topurification of crude furan 2,5-dicarboxylic acid by mild hydrogenation.

BACKGROUND OF THE INVENTION

Aromatic dicarboxylic acids such as terephthalic acid and isophthalicacid are used to produce a variety of polyester products, importantexamples of which are poly (ethylene terephthalate) and its copolymers.These aromatic dicarboxylic acids are synthesized by the catalyzedautoxidation of the corresponding dialkyl aromatic compounds which areobtained from fossil fuels (US 2006/0205977 A1). There is a growinginterest in the use of renewable resources as feed stocks for thechemical industries mainly due to the progressive reduction of fossilreserves and their related environmental impacts.

Furan 2,5-dicarboxylic acid (“FDCA”) is a versatile intermediateconsidered as a promising closest biobased alternative to terephthalicacid and isophthalic acid. It is synthesized by the catalytic oxidationof 5-(hydroxymethyl)furfural (5-HMF) as shown in equation 1 below; or bythe catalytic oxidation of 5-HMF esters (5-R(CO)OCH₂-furfural whereR=alkyl, cycloalkyl and aryl) as shown in equation 2 below; or by thecatalytic oxidation of 5-HMF ethers (5-R′OCH₂-furfural, where R′=alkyl,cycloalkyl and aryl) as shown in equation 3 below; or by the catalyticoxidation of 5-alkyl furfurals (5-R″-furfural, where R″=alkyl,cycloalkyl and aryl) as shown in equation 4 below; in each case using aCo/Mn/Br catalyst system. Mixed feedstocks of 5-HMF and 5-HMF esters,mixed feedstocks of 5-HMF and 5-HMF ethers, and mixed feedstocks of5-HMF and 5-alkyl furfurals can also be used.

We have found that the above reactions work well. However a number ofimpurities are produced, particularly mono-carboxylic acid species suchas 5-formyl furan-2-carboxyic acid (FFCA). These mono-carboxylic acidsare not desirable since they terminate the chain growth of a polymerresulting in lower polymer viscosity. If colored bodies are present inthe crude FDCA or remaining in the product FDCA, these colored bodiescarry through to compounds or polymers using the FDCA as a reactivemonomer to thereby color the compound or polymer. Therefore, it isnecessary to purify the crude FDCA to remove the color bodies whileminimizing the presence of FFCA in the product FDCA.

In process for the manufacture of terephthalic acid, one conventionalmethod of purifying crude terephthalic acid (CTA) is to produce purifiedterephthalic acid (PTA) is by subjecting the CTA to a hydrogenationtreatment, where 4-CBA (a chain terminator) is hydrogenated topara-toluic acid and color bodies are hydrogenated to colorless solidcompounds. To accomplish purification by hydrogenation, solid CTAparticles are typically dissolved in a solvent (e.g., water), and theresulting solution is subjected to liquid-phase hydrogenation in thepresence of a hydrogenation catalyst. Although effective to reduceyellowness, purification of CTA by hydrogenation can be expensivebecause it is conducted under high reaction temperatures therebyconsuming a large amount of energy and conducted under high hydrogenpartial pressure thereby consuming a large amount of hydrogen.

Thus, there remains a need to effectively reduce the color bodies incrude FDCA without consuming large amount of energy or hydrogen in theprocess.

SUMMARY OF THE INVENTION

In this invention we disclose a process to make a product FDCA (pFDCA)that has been purified by catalytic hydrogenation under mild conditions.

In particular there is now provided a process for purifying a crudefuran 2,5-dicarboxylic acid composition (cFDCA) comprising:

-   -   a) providing a cFDCA composition comprising furan        2,5-dicarboxylic acid (FDCA) solids, 5-formyl furan-2-carboxyic        acid (FFCA), and a oxidation solvent composition;    -   b) combining a hydrogenation solvent composition with said FDCA        solids and dissolving at least a portion of the FDCA solids to        thereby produce a solvated FDCA (sFDCA) composition comprising        dissolved FDCA, the hydrogenation solvent composition, and FFCA;    -   c) in a hydrogenation reaction zone, hydrogenating the sFDCA at        a temperature within a range of 130° C. to 225° C. by contacting        the sFDCA composition with hydrogen in the presence of a        hydrogenation catalyst to thereby hydrogenate FFCA and produce a        furan 2,5-dicarboxylic acid composition (hFDCA) comprising a        hydrogenated FFCA species, dissolved FDCA, and said        hydrogenation solvent; and    -   e) separating at least a portion of the dissolved FDCA from the        hFDCA composition to obtain a product FDCA (pFDCA) composition.

Desirably, a pFDCA composition is provided that has been purified byhydrogenation at a temperature within a range of 130° C. to 225° C. bycontacting the sFDCA composition with hydrogen in the presence of ahydrogenation catalyst under a hydrogen partial pressure within a rangeof 10 psi to 900 psi.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts the solubility of FDCA in water at differenttemperatures.

DETAILED DESCRIPTION OF THE INVENTION

It should be understood that the following is not intended to be anexclusive list of defined terms. Other definitions may be provided inthe foregoing description, such as, for example, when accompanying theuse of a defined term in context.

As used herein, the terms “a,” “an,” and “the” mean one or more.

As used herein, the term “and/or,” when used in a list of two or moreitems, means that any one of the listed items can be employed by itselfor any combination of two or more of the listed items can be employed.For example, if a composition is described as containing components A,B, and/or C, the composition can contain A alone; B alone; C alone; Aand B in combination; A and C in combination, B and C in combination; orA, B, and C in combination.

As used herein, the terms “comprising,” “comprises,” and “comprise” areopen-ended transition terms used to transition from a subject recitedbefore the term to one or more elements recited after the term, wherethe element or elements listed after the transition term are notnecessarily the only elements that make up the subject.

As used herein, the terms “having,” “has,” “contain,” “including,”“includes,” “include,” and “have” have the same open-ended meaning as“comprising,” “comprises,” and “comprise” provided above.

The present description uses numerical ranges to quantify certainparameters relating to the invention. It should be understood that whennumerical ranges are provided, such ranges are to be construed asproviding literal support for claim limitations that only recite thelower value of the range as well as claim limitations that only recitethe upper value of the range. For example, a disclosed numerical rangeof 10 to 100 provides literal support for a claim reciting “greater than10” (with no upper bounds) and a claim reciting “less than 100” (with nolower bounds) and provided literal support for and includes the endpoints of 10 and 100.

The present description uses specific numerical values to quantifycertain parameters relating to the invention, where the specificnumerical values are not expressly part of a numerical range. It shouldbe understood that each specific numerical value provided herein is tobe construed as providing literal support for a broad, intermediate, andnarrow range. The broad range associated with each specific numericalvalue is the numerical value plus and minus 60 percent of the numericalvalue, rounded to two significant digits. The intermediate rangeassociated with each specific numerical value is the numerical valueplus and minus 30 percent of the numerical value, rounded to twosignificant digits. The narrow range associated with each specificnumerical value is the numerical value plus and minus 15 percent of thenumerical value, rounded to two significant digits. For example, if thespecification describes a specific temperature of 62° F., such adescription provides literal support for a broad numerical range of 25°F. to 99° F. (62° F.+/−37° F.), an intermediate numerical range of 43°F. to 81° F. (62° F.+/−19° F.), and a narrow numerical range of 53° F.to 71° F. (62° F.+/−9° F.). These broad, intermediate, and narrownumerical ranges should be applied not only to the specific values, butshould also be applied to differences between these specific values.Thus, if the specification describes a first pressure of 110 psia and asecond pressure of 48 psia (a difference of 62 psi), the broad,intermediate, and narrow ranges for the pressure difference betweenthese two streams would be 25 to 99 psi, 43 to 81 psi, and 53 to 71 psi,respectively

All amounts are by weight unless otherwise specified. All amounts byweight are based on the weight of the whole composition streamcontaining the ingredient in question rather than a part of thatcomposition or a different stream altogether, unless otherwise noted.All stated amounts in ppm are by weight (ppmw) unless otherwise noted.

There is provided a crude FDCA (cFDCA) composition comprising furan2,5-dicarboxylic acid (FDCA) solids, 5-formyl furan-2-carboxyic acid(FFCA), and a oxidation solvent composition. This composition may beprovided in a variety of ways. One technique is described as follows.

An oxidizable composition is fed to an oxidation zone, where theoxidizable composition contains a compound having a furan moiety. Thefuran moiety can be represented by the structure:

The compounds having a furan moiety are such that, upon oxidation, formcarboxylic acid functional groups on the compound. Examples of compoundshaving furan moieties include 5-(hydroxymethyl)furfural (5-HMF), andderivatives of 5-HMF. Such derivatives include esters of 5-HMF, such asthose represented by the formula 5-R(CO)OCH₂-furfural where R=alkyl,cycloalkyl and aryl groups having from 1 to 8 carbon atoms, or 1-4carbon atoms or 1-2 carbon atoms; ethers of 5-HMF represented by theformula 5-R′OCH₂-furfural, where R′=alkyl, cycloalkyl and aryl havingfrom 1 to 8 carbon atoms, or 1-4 carbon atoms or 1-2 carbon atoms);5-alkyl furfurals represented by the formula 5-R″-furfural, whereR″=alkyl, cycloalkyl and aryl having from 1 to 8 carbon atoms, or 1-4carbon atoms or 1-2 carbon atoms). Thus the oxidizable composition cancontain mixtures of 5-HMF and 5-HMF esters; 5-HMF and 5-HMF ethers;5-HMF and 5-alkyl furfurals, or mixtures of 5-HMF and its esters,ethers, and alkyl derivatives.

The oxidizable composition, in addition to 5-(hydroxymethyl)furfural(5-HMF) or an of its derivatives, may also contain5-(acetoxymethyl)furfural (5-AMF) and 5-(ethoxymethyl)furfural (5-EMF).

Specific examples of 5-HMF derivatives include those having thefollowing structures:

Preferred 5-HMF Derivative Feeds

An oxidizable composition is fed to a primary oxidation zone and reactedin the presence of a oxidation solvent composition, a catalyst system,and a gas comprising oxygen, to generate a crude dicarboxylic acidstream comprising furan-2,5-dicarboxylic acid (FDCA).

For example, the oxidizable composition containing 5-HMF, or itsderivatives, or combinations thereof, are oxidized with O₂ in amulti-step reaction to form FDCA with 5-formyl furan-2-carboxylic acid(FFCA) as a key intermediate, represented by the following sequence:

If desired, the oxygen gas stream comprising oxygen, an oxidationsolvent composition stream, and the oxidizable stream can be fed to aprimary oxidation zone as separate streams. Or, an oxygen streamcomprising oxygen as one stream and an oxidizable stream comprisingoxidation solvent composition, catalyst, and oxidizable compounds as asecond stream can be fed to the primary oxidation zone. Accordingly, theoxidation solvent composition, oxygen gas comprising oxygen, catalystsystem, and oxidizable compounds can be fed to the primary oxidizationzone as separate and individual streams or combined in any combinationprior to entering the primary oxidization zone wherein these feedstreams may enter at a single location or in multiple locations into theprimary oxidizer zone.

The catalyst can be a homogenous catalyst soluble in the oxidationsolvent composition or a heterogeneous catalyst. The catalystcomposition is desirably soluble in the oxidation solvent compositionunder reaction conditions, or it is soluble in the reactants fed to theoxidation zone. Preferably, the catalyst composition is soluble in theoxidation solvent composition at 40° C. and 1 atm, and is soluble in theoxidation solvent composition under the reaction conditions.

Suitable catalysts components comprise at least one selected from, butare not limited to, cobalt, bromine and manganese compounds. Preferablya homogeneous catalyst system is selected. The preferred catalyst systemcomprises cobalt, manganese and bromine.

The cobalt atoms may be provided in ionic form as inorganic cobaltsalts, such as cobalt bromide, cobalt nitrate, or cobalt chloride, ororganic cobalt compounds such as cobalt salts of aliphatic or aromaticacids having 2-22 carbon atoms, including cobalt acetate, cobaltoctanoate, cobalt benzoate, cobalt acetylacetonate, and cobaltnaphthalate. The oxidation state of cobalt when added as a compound tothe reaction mixture is not limited, and includes both the +2 and +3oxidation states.

The manganese atoms may be provided as one or more inorganic manganesesalts, such as manganese borates, manganese halides, manganese nitrates,or organometallic manganese compounds such as the manganese salts oflower aliphatic carboxylic acids, including manganese acetate, andmanganese salts of beta-diketonates, including manganeseacetylacetonate.

The bromine component may be added as elemental bromine, in combinedform, or as an anion. Suitable sources of bromine include hydrobromicacid, sodium bromide, ammonium bromide, potassium bromide, andtetrabromoethane. Hydrobromic acid or sodium bromide may be preferredbromine sources.

The amount of bromine atoms desirably ranges from at least 300 ppm, orat least 2000 ppm, or at least 2500 ppm, or at least 3000 ppm, or atleast 3500 ppm, or at least 3750, ppm and up to 4500 ppm, or up to 4000ppm, based on the weight of the liquid in the reaction medium of theprimary oxidation zone. Bromine present in the amount of 2500 ppm to4000 ppm, or 3000 ppm to 4000 ppm are especially desirable to promotehigh yield.

The amount of cobalt atoms can range from at least 500 ppm, or at least1500 ppm, or at least 2000 ppm, or at least 2500 ppm, or at least 3000ppm, and up to 6000 ppm, or up to 5500 ppm, or up to 5000 ppm, based onthe weight of the liquid in the reaction medium of the primary oxidationzone. Cobalt present in an amount of 2000 ppm to 6000 ppm, or 2000 ppmto 5000 ppm is especially desirable to promote high yield.

The amount of manganese atoms can range from 2 ppm, or at least 10 ppm,or at least 30 ppm, or at least 50 ppm, or at least 70 ppm, or at least100 ppm, and in each case up to 600 ppm, or up to 500 ppm or up to 400ppm, or up to 350 ppm, or up to 300 ppm, or up to 250 ppm, based on theweight of the liquid in the reaction medium of the primary oxidationzone. Manganese present in an amount ranging from 30 ppm to 400 ppm, or70 ppm to 350 ppm, or 100 ppm to 350 ppm is especially desirable topromote high yield.

The weight ratio of cobalt atoms to manganese atoms in the reactionmixture can be from 1:1 to 400:1 or 10:1 to about 400:1. A catalystsystem with improved Co:Mn ratio can lead to high yield of FDCA. Toincrease the yield of FDCA, when the oxidizable composition fed to theoxidation reactor comprises 5-HMF, then the cobalt to manganese weightratio is at least 10:1, or at least 15:1, or at least 20:1, or at least25:1, or at least 30:1, or at least 40:1 or at least 50:1, or at least60:1, and in each case up to 400:1. However, in the case where theoxidizable composition comprises esters of 5-HMF, ethers of 5-HMF, or5-alkyl furfurals, or mixtures of any of these compounds together orwith 5-HMF, the cobalt to manganese weight ratio can be lowered whilestill obtaining high yield of FDCA, such as a weight ratio of Co:Mn ofat least 1:1, or at least 2:1, or at least 5:1, or at least 9:1, or atleast 10:1, or at least 15:1, or at least 20:1, or at least 25:1, or atleast 30:1, or at least 40:1, or at least 50:1, or at least 60:1 and ineach case up to 400:1.

The weight ratio of cobalt atoms to bromine atoms is desirably at least0.7:1, or at least 0.8:1, or at least 0.9:1, or at least 1:1, or atleast 1.05:1, or at least 1.2:1, or at least 1.5:1, or at least 1.8:1,or at least 2:1, or at least 2.2:1, or at least 2.4:1, or at least2.6:1, or at least 2.8:1, and in each case up to 3.5, or up to 3.0, orup to 2.8.

The weight ratio of bromine atoms to manganese atoms is from about 2:1to 500:1.

Desirably, the weight ratio of cobalt to manganese is from 10:1 to400:1, and the weight ratio of cobalt to bromine atoms ranges from 0.7:1to 3.5:1. Such a catalyst system with improved Co:Mn and Co:Br ratio canlead to high yield of FDCA (minimum of 90%), decrease in the formationof impurities (measured by b*) causing color in the downstreampolymerization process while keeping the amount of CO and CO₂ (carbonburn) in the off-gas at a minimum.

Desirably, the amount of bromine present is at least 1000 ppm and up to3500 ppm, and the weight ratio of bromine to manganese is from 2:1 to500:1. This combination has the advantage of high yield and low carbonburn.

Desirably, the amount of bromine present is at least 1000 ppm and up to3000 ppm, and the amount of cobalt present is at least 1000 ppm and upto 3000 ppm, and the weight ratio of cobalt to manganese is from 10:1 to100:1. This combination has the advantage of high yield and low carbonburn.

Suitable oxidation solvent compositions include aliphatic oxidationsolvent compositions. In an embodiment of the invention, the oxidationsolvent compositions are aliphatic carboxylic acids which include, butare not limited to, C₂ to C₆ monocarboxylic acids, e.g., acetic acid,propionic acid, n-butyric acid, isobutyric acid, n-valeric acid,trimethylacetic acid, caprioic acid, and mixtures thereof.

The most common oxidation solvent composition used for the oxidation isan aqueous acetic acid solution, typically having an acetic acidconcentration of 80 to 99 wt. % before adding it to the oxidation zone.In especially preferred embodiments, the oxidation solvent compositionas added comprises a mixture of water and acetic acid which has a watercontent of 0% to about 15% by weight. Additionally, a portion of theoxidation solvent composition feed to the primary oxidation reactor maybe obtained from a recycle stream obtained by displacing about 80 to 90%of the mother liquor taken from the crude reaction mixture streamdischarged from the primary oxidation reactor with fresh, wet aceticacid containing about 0 to 15% water.

The oxidizing gas stream comprises oxygen. Examples include, but are notlimited to, air and purified oxygen. The amount of oxygen in the primaryoxidation zone ranges from about 5 mole % to 45 mole %, 5 mole % to 60mole %, 5 mole % to 80 mole %.

The temperature of the reaction mixture in the primary oxidation zonecan vary from about 100° C. to about 220° C. The temperature of thereaction mixture in the primary oxidation zone is at least 100° C., orat least 105° C., or at least 110° C., or at least 115° C., or at least120° C., or at least 125° C., or at least 130° C., or at least 135° C.,or at least 140° C., or at least 145° C., or at least 150° C., or atleast 155° C., or at least 160° C., and can be as high as 220° C., or upto 210° C., or up to 200° C., or up to 195° C., or up to 190° C., or upto 180° C., or up to 175° C., or up to 170° C., or up to 165° C., or upto 160° C., or up to 155° C., or up to 150° C., or up to 145° C., or upto 140° C., or up to 135° C., or up to 130° C. In other embodiments, thetemperate ranges from 105° C. to 180° C., or from 105° C. to 175° C., orfrom 105° C. to 170° C., or from 105° C. to 165° C., or from 105° C. to160° C., or from 105° C. to 155° C., or from 105° C. to 150° C., or from110° C. to 180° C., or from 110° C. to 175° C., or from 110° C. to 170°C., or from 110° C. to 165° C., or from 110° C. to 160° C., or from 110°C. to 155° C., or from 110° C. to 150° C., or from 110° C. to 145° C.,or from 115° C. to 180° C., or from 115° C. to 175° C., or from 115° C.to 170° C., or from 115° C. to 165° C., or from 115° C. to 160° C., orfrom 115° C. to 155° C., or from 110° C. to 150° C., or from 115° C. to145° C., or from 120° C. to 180° C., or from 120° C. to 175° C., or from120° C. to 170° C., or from 120° C. to 165° C., or from 120° C. to 160°C., or from 120° C. to 155° C., or from 120° C. to 150° C., or from 120°C. to 145° C., or from 125° C. to 180° C., or from 125° C. to 175° C.,or from 125° C. to 170° C., or from 125° C. to 165° C., or from 125° C.to 160° C., or from 125° C. to 155° C., or from 125° C. to 150° C., orfrom 125° C. to 145° C., or from 130° C. to 180° C., or from 130° C. to175° C., or from 130° C. to 170° C., or from 130° C. to 165° C., or from130° C. to 160° C., or from 130° C. to 155° C., or from 130° C. to 150°C., or from 130° C. to 145° C., or from 135° C. to 180° C., or from 135°C. to 175° C., or from 135° C. to 170° C., or from 135° C. to 165° C.,or from 135° C. to 160° C., or from 135° C. to 155° C., or from 135° C.to 150° C., or from 135° C. to 145° C., or from 140° C. to 180° C., orfrom 140° C. to 175° C., or from 140° C. to 170° C., or from 140° C. to170° C., or from 140° C. to 165° C., or from 140° C. to 160° C., or from140° C. to 155° C., or from 140° C. to 150° C., or from 140° C. to 145°C., or from 145° C. to 180° C., or from 145° C. to 175° C., or from 145°C. to 170° C., or from 145° C. to 170° C., or from 145° C. to 165° C.,or from 145° C. to 160° C., or from 145° C. to 155° C., or from 145° C.to 150° C., or from 150° C. to 180° C., or from 150° C. to 175° C., orfrom 150° C. to 170° C., or from 150° C. to 165° C., or from 150° C. to160° C., or from 150° C. to 155° C., or from 155° C. to 180° C., or from155° C. to 175° C., or from 155° C. to 170° C., or from 155° C. to 165°C., or from 155° C. to 160° C., or from 160° C. to 180° C., or from 160°C. to 175° C., or from 160° C. to 170° C., or from 160° C. to 165° C.,or from 165° C. to 180° C., or from 165° C. to 175° C., or from 165° C.to 170° C., or from 165° C. to 180° C., or from 165° C. to 175° C., orfrom 165° C. to 170° C., or from 170° C. to 180° C., or from 170° C. to175° C., or from 175° C. to 180° C.

To minimize carbon burn, it is desired that the temperature of thereaction mixture is not greater than 165° C., or not greater than 160°C. The contents of the oxidizer off gas comprise COx, wherein x is 1 or2, and the amount of COx in the oxidizer off gas is less than 0.05 molesof COx per mole of the total oxidizable feed to the reaction medium, orno more than 4 moles of COx per mole of the total oxidizable feed to thereaction medium, or no more than 6 moles of COx per mole of the totaloxidizable feed to the reaction medium. The carbon burn as determined bythe COx generation rate can be calculated as follows: (moles of CO+molesof CO2)/moles of oxidizable feed. The low carbon burn generation rate isachievable by the combination of low reaction temperature, and the molarweight ratios of the catalyst components as described above.

The oxidation reaction can be conducted under a pressure ranging from 40to 300 psia. A bubble column is desirably operated under a pressureranging from 40 psia to 150 psia. In a stirred tank vessel, the pressureis desirably set to 100 psia to 300 psia.

Oxidizer off gas stream containing COx (CO and CO₂), water, nitrogen,and vaporized oxidation solvent composition, is routed to the oxidizeroff gas treatment zone to generate an inert gas stream, liquid streamcomprising water, and a recovered oxidation solvent composition streamcomprising condensed oxidation solvent composition. In one embodiment,the oxidizer off gas stream can be fed to directly, or indirectly afterseparating condensables such as oxidation solvent composition fromnon-condensables such as COx and nitrogen in a separation column (e.g.distillation column with 10-200 trays), to an energy recovery devicesuch as a turbo-expander to drive an electric generator. Alternativelyor in addition, the oxidizer off gas stream can be fed to a steamgenerator before or after the separation column to generate steam, andif desired, may then be fed to a turbo-expander and pre-heated prior toentry in the expander if necessary to ensure that the off gas does notcondense in the turbo-expander.

The oxidation can be conducted in a continuous stirred tank reactor orin a bubble column reactor.

The FDCA formed by the oxidation reaction desirably precipitates out ofthe reaction mixture. The reaction mixture comprises the oxidizablecomposition, oxidation solvent composition, and catalyst if ahomogeneous catalyst is used, otherwise it comprises the oxidizablecomposition and oxidation solvent composition.

The product of the oxidation reaction is a crude dicarboxylic acidstream (“cFDCA”) comprising solids, said solids comprising FDCA; anoxidation solvent composition; and the intermediate product 5-formylfuran-2-carboxylic acid (“FFCA”). The cFDCA may also contain some amountof FDCA dissolved in the oxidation solvent composition and if used, someof the homogeneous catalyst system. The cFDCA is colored as a result ofthe production of color by-products. The presence of color bodies can bedetected by measuring the b* of the cFDCA composition. The cFDCAcomposition may also contain mono-carboxylic acid FFCA which is notdesirable because it acts to terminate chain growth in a polymerizationreaction using an FDCA composition as a reactant.

The cFDCA composition comprises:

-   -   a) solids in an amount of at least 5 wt. %, or at least 10 wt %,        or at least 15 wt. %, or at least 20 wt. %, or at least 25 wt.        %, or at least 28 wt. %, or at least 30 wt. %, or at least 32        wt. %, or at least 35 wt. %, or at least 37 wt. %, or at least        40 wt. %, based on the weight of the cFDCA composition. While        there is no upper limit, as a practice the amount will not        exceed 60 wt. %, or no greater than 55 wt. %, or no greater than        50 wt. %, or no greater than 45 wt. %, or not greater than 43        wt. %, or not greater than 40 wt %, or not greater than 39 wt %,        based on the weight of the cFDCA composition;    -   b) of the solids in the crude dicarboxylic acid stream, it is        desirable that at least 70 wt. %, or at least 80 wt. %, or at        least 85 wt. %, or at least 90 wt. %, or at least 95 wt. %, or        at least 96 wt. %, or at least 97 wt. %, or at least 98 wt. %,        or at least 99 wt. % of the solids in each case is FDCA based on        the weight of the solids;    -   c) at least 0.1 wt. % FFCA, or at least 0.2 wt. % FFCA, or at        least 0.3 wt. % FFCA, or at least 0.35 wt. % FFCA, or at least        0.4 wt. % FFCA, and can contain large amounts of FFCA, such as        up to 5 wt. %, or up to 4 wt. %, or up to 3 wt %, or up to 2 wt.        %, based on the weight of the cFDCA composition.

Optionally, in addition to FFCA, other by-products can also be presentin the cFDCA composition such as color bodies. Color bodies can beformed from impurities present in the oxidizable composition, e.g. 5-HMFcomposition fed into the oxidiation zone, or degradation productsproduced in the course of the oxidation of the 5-HMF composition. Otherby-products besides FFCA present in the cFDCA composition can include,for example, compounds such as 2,5-diformylfuran, levulinic acid,succinic acid, acetoxyacetic acid, 5-(ethoxycarbonyl)furan-2-carboxylicacid (“EFCA”), and their oxidation derivatives. 2,5 diformylfuran can bepresent, if at all, in an amount of 0 wt % to about 0.2 wt %; levulinicacid in an amount ranging from 0 wt % to 1 wt. % or up to 0.5 wt %;succinic acid in an amount ranging from 0 wt % to 1 wt. %, or up to 0.5wt %; EFCA in an amount of greater than 0, or at least 0.05 wt %, or atleast 0.1 wt %, or at least 0.5 wt % and in each case up to about 4 wt%, or up to about 3.5 wt %, or up to 3 wt. %, or up to 2.5 wt %, or upto 2 wt. %; acetoxyacetic acid in an amount ranging from 0 wt % to 0.5wt %, and a cumulative amount of the by-products (including FFCA) can bepresent in an amount ranging from greater than 0 wt. %, or at least 0.1wt. %, or at least 0.5 wt. %, or at least 1 wt. %, or at least 2 wt. %,an up to 30 wt. %, or up to 20 wt. %, or up to 15 wt. %, or up to 10 wt.%, or up to 5 wt. %, or up to 3 wt. %, or up to 2 wt. %, or up to 1 wt.%, in each case based on the weight of cFDCA composition.

Because some of the by-products present in the cFDCA, the cFDCAcomposition may be color bodies and/or the cFDCA composition may containFFCA which is a chain terminating compound, it is desirable to subjectthe cFDCA composition to a process for the production of a low colorproduct FDCA composition. The cFDCA composition may have a high b*.While the b* value is not limited, the cFDCA composition will typicallyhave a b* of more than 3, or more than 4, or more than 5, or more than6, or more than 7, and may have a b* as high as 50, or up to 40, or upto 30, or up to 20, or up to 19, or up to 18, or up to 17, or up to 16,or up to 15, or up to 10, or up to 8, or up to 6. Even with a b* up to5, or up to 4 it is desirable to purify the cFDCA composition to lowerthe b* color. Even though the b* may not be an important considerationfor a particular application, some applications require chainpropagation and therefore it is desirable to purify the cFDCAcomposition to reduce the amount of FFCA present.

While the amount of FFCA present in the cFDCA composition is notlimited, the process of the invention is effective to reduce the amountof FFCA present in the cFDCA composition, relative to the amount of FFCAin the product FDCA composition, by a factor of at least 2×, or at least10×, or at least 100×, or at least 200×, or at least 300×, or at least350×, or at least 400×, or at least 500×, or at least 750×, or at least900×, or at least 1000×, or at least 1500×, calculated as:

-   -   x reduction=ppm FFCA in cFDCA divided by ppm FFCA in product        FDCA composition (where FFCA detected in the product FDCA        composition at a value below 1 ppm, or undetectable by virtue of        its absence or below the detection limit of an analytical        instrument, is, for purposes of this calculation, taken as a        value of 1 ppm).

The yield of FDCA in the cFDCA composition, on a solids basis, is atleast 60%, or at least 65%, or at least 70%, or at least 72%, or atleast 74%, or at least 76%, or at least 78%, or at least 80%, or atleast 81%, or at least 82%, or at least 83%, or at least 84%, or atleast 85%, or at least 86%, or at least 87%, or at least 88%, or atleast 89%, or at least 90%, or at least 91%, or at least 92%, or atleast 94%, or at least 95%, and up to 99%, or up to 98%, or up to 97%,or up to 96%, or up to 95%, or up to 94%, or up to 93%, or up to 92%, orup to 91%, or up to 90%, or up to 89%. For example, the yield can rangefrom 70% up to 99%, or 74% up to 98%, or 78% up to 98%, or 80% up to98%, or 84% up to 98%, or 86% up to 98%, or 88% up to 98%, or 90% up to98%, or 91% up to 98%, or 92% up to 98%, or 94% up to 98%, or 95% up to99%.

Yield is defined as mass of FDCA obtained divided by the theoreticalamount of FDCA that should be produced based on the amount of rawmaterial use. For example, if one mole or 126.11 grams of 5-HMF areoxidized, it would theoretically generate one mole or 156.09 grams ofFDCA. If for example, the actual amount of FDCA formed is only 150grams, the yield for this reaction is calculated to be=(150/156.09)times 100, which equals a yield of 96%. The same calculation applies foroxidation reaction conducted using 5-HMF derivatives or mixed feeds.

In a second step, the composition of the oxidation solvent compositionin the cFDCA composition can be changed by combining a hydrogenationsolvent composition with the FDCA solids and dissolving at least aportion of the FDCA solids to thereby produce a solvated FDCA (sFDCA)composition comprising dissolved furan 2,5-dicarboxylic acid (FDCA), thehydrogenation solvent composition, and 5-formyl furan-2-carboxyic acid(FFCA). The sFDCA composition may contain some solids or may be asolution. This step is described further.

The oxidation solvent composition is desirably replaced at least in partwith a hydrogenation solvent to avoid producing a large amount ofundesirable by-products of the oxidation solvent during hydrogenation.For example, hydrogenation can convert the oxidation solvent acetic acidinto ethanol, which then results in having to remove ethanol from thehydrogenated FDCA composition. To avoid the production of anysignificant quantities of additional by-products that necessitateremoval, the oxidation solvent composition is changed or partially orfully replaced before hydrogenation is conducted.

To effect the change or partial or full replacement, a hydrogenationsolvent composition is combined with, and desirably added to, the cFDCAcomposition. The hydrogenation solvent composition is different than theoxidation solvent composition. The difference can be attributed to theuse of a hydrogenation solvent composition containing ingredients whichare not present in the oxidation solvent composition, or may contain atleast one of the same ingredients as in the oxidation solventcomposition but where the molar ratio of the solvents within theoxidation solvent composition are different than the molar ratio ofsolvents within the hydrogenation solvent composition. An example of thelatter is a oxidation solvent composition that contains a mixture of asmall amount of water in acetic acid at a molar ratio of 2:8, while thehydrogenation solvent composition may contain water at a higher molarratio (e.g. greater than 2:8 which would also include all water 100:0).Both solvent compositions contain water but each at different molarratios to either exchange or dilute a portion of one of the ingredientsin the oxidation solvent composition (e.g. acetic acid solvent), therebyshifting the solvent composition to one which is more desirable underhydrogenation reaction conditions.

After the solvent swap (the term also includes dilution), the overallconcentration of the hydrogenation solvent composition relative to theweight of the solvated FDCA composition can be higher or lower than theconcentration of the oxidation solvent composition relative to theweight of the cFDCA composition. In one embodiment, the concentration ofhydrogenation solvents in the sFDCA composition is higher than theconcentration of oxidation solvents in the cFDCA solution.

The solvent swap systems can include a solid/liquid separation systemand optionally an evaporation zone prior to feeding the solid/liquidseparation system. The evaporator, if used, is operated to remove asubstantial portion of the oxidation solvent (e.g., acetic acid andwater) from cFDCA composition. The evaporated oxidation solvent isdischarged from the evaporator. The evaporation zone operates to flashthe cFDCA composition and cool the cFDCA by evaporative cooling. Theevaporator can include multiple zones of evaporation. The evaporationzone can be maintained at a temperature in the range of from about 25 toabout 170° C., or in the range of from about 75 to about 150° C.

A concentrated slurry is discharged from the evaporator and fed to thesolid-liquid separation zone. Alternatively, the cFDCA stream dischargedfrom the oxidation zone can be fed into the solid dissolved separationzone without first passing through an evaporator. If an evaporator isused, the concentration of solids in the concentrated slurry isdesirably increased by at least 20%, or at least 30%, or at least 50%over the concentration of solids in the cFDCA discharged from theoxidation zone. Further, if desired, a portion or all of the feed to theevaporator, such as a flash vessel, can be directed into a by-passstream and fed directly to the solid-liquid separation zone withoutentering into the evaporator.

The concentrated slurry can be introduced into solid/liquid separatorwhere at least a portion of the liquid mother liquor is removed from theconcentrated slurry. The removed mother liquor is discharged fromsolid/liquid separator and the resulting wet cake containing residues ofthe oxidation solvent is washed with at least one wash solvent streamthat is desirably the same as the hydrogenation solvent (e.g. water) toremove substantially all of the residual oxidation solvent remaining onthe wet cake.

The functions of solid liquid separation and washing the cFDCA may beaccomplished in a single solid-liquid separation device or multiplesolid-liquid separation devices. The solid-liquid separation zonecomprises at least one solid-liquid separation device capable ofseparating solids and liquids. Additionally, the solid liquid separationdevice can also perform the function of washing the solids with a washsolvent stream which is the same as the hydrogenation solvent, e.g.water.

Equipment suitable for the solid liquid separation zone can typically becomprised of, but not limited to, the following types of devices:centrifuges of all types including but not limited to decanter and discstack centrifuges, cross flow filters, solid bowl centrifuges, cyclone,rotary drum filter, belt filter, pressure leaf filter, candle filter, acontinuous pressure drum filter, or more specifically a continuousrotary pressure drum filter. The solid-liquid separator may be operatedin continuous or batch mode, although it will be appreciated that forcommercial processes, the continuous mode is preferred. A suitablepressure filter which can be employed as the solid/liquid separator is aBHS-FEST™, available from BHS-WERK, Sonthofen, D-8972, Sonthofen, WestGermany.

The temperature of the wash solvent can range from 20° C. to 180° C., or40° C. and 150° C., or 50° C. to 130° C. The amount of wash solvent usedis defined as the wash ratio and equals the mass of wash divided by themass of solids on a batch or continuous basis. The wash ratio can rangefrom about 0.3 to about 5, about 0.4 to about 4, and preferably fromabout 0.5 to 3.

The wash feed is desirably formed primarily of water. Most preferablythe wash feed consists essentially of water. There may exist more thanone wash zone.

The washed cFDCA cake is discharged from the solid liquid separationzone and fed to a dissolution zone for dissolving the washed cFDCA cakeinto a hydrogenation solvent composition useful in hydrogenationreactions. The source of the hydrogenation solvent composition can comefrom the wash solvent or from the dissolution solvent stream providedinto the dissolution zone or both.

The hydrogenation solvent composition desirably comprises a solventwhich dissolves at least a portion of the FDCA solids under conditionsused in the hydrogenation reaction zone and which does not itselfconvert to other products which must be separated in any appreciableamount, e.g more than 20% conversion of the types of products requiringremoval. Suitable hydrogenation solvent compositions include water andsteam. Desirably, the hydrogenation solvent composition comprises atleast 80 wt. % water, or at least 90 wt. % water, or at least 95 wt. %water, or at least 99 wt. % water, or at least 100 wt. % water.

In the dissolution zone, it may be necessary to elevate the temperatureof the cFDCA solids when combined with the hydrogenation solventcomposition to dissolve at least a portion of the FDCA solids into thehydrogenation solvent composition. The hydrogenation solvent and washedcFDCA solids are desirably combined at a solvent-to-solids weight ratioin the range of from about 0.5:1 to about 50:1, or in the range of from1:1 to 20:1, or in the range of from 1:1 to 15:1, or in the range offrom 1:1 to 10:1, or in the range of from 1.5:1 to 5:1.

Suitable dissolution temperatures are those effective to dissolve thedesired amount of FDCA solids into solution. The hydrogenation solventcomposition may be added at (by pre-heating) or heated in thedissolution zone to a temperature of at least 120° C. under a pressureand time sufficient to allow for at least 80 wt. % dissolution, althoughto reduce the time required for dissolution, it is desirable that thehydrogenation solvent composition temperature is at least 130° C., or atleast 135° C., or at least 140° C., or at least 150° C. Thehydrogenation solvent temperature does not need to exceed 240° C., or220° C., or 200° C., or even 190° C., or even 180° C. As seen in FIG. 1,the solubility of FDCA in water at ambient pressure increasesdramatically as the temperature of the water increases beyond 130° C.

It is desired to dissolve at least 80 wt. %, or at least 90 wt. %, or atleast 95 wt. %, or at least 98 wt. %, or at least 99 wt. % or at least99.5 wt. % of the solids in the cFDCA solution to produce a solvatedFDCA composition (“sFDCA”). The sFDCA composition comprises dissolvedfuran 2,5-dicarboxylic acid (FDCA), hydrogenation solvent composition inan amount of at least 30 wt. % based on the weight of the sFDCAcomposition, and 5-formyl furan-2-carboxyic acid (FFCA).

An example of the sFDCA composition comprises:

-   -   a) less than 5 wt. %, or less than 4 wt. %, or less than 3 wt.        %, or less than 2 wt. %, or less than 1 wt. %, or less than 0.5        wt. %, or less than 0.1 wt. %, or less than 0.01 wt. % solids;    -   b) dissolved FDCA in an amount of greater than 0, or at least 1        wt. %, or at least 2 wt. %, or at least 5 wt. %, or at least 7        wt. %, or at least 9 wt. %, or at least 10 wt. %, or at least 12        wt. %, or at least 15 wt. %, based on the weight of the sFDCA        composition. The upper limit is not particularly limited, but        amount of up to 50 wt. %, or up to 45 wt. %, or up to 40 wt. %,        or up to 35 wt. %, or up to 30 wt. %, or up to 25 wt. %, or up        to 20 wt. %, or up to 15 wt. %, or up to 12 wt. %, based on the        weight of the sFDCA composition, are useful; and    -   c) a hydrogenation solvent in an amount of at least 30 wt. %, or        at least 35 wt. %, or at least 40 wt. %, or at least 45 wt. %,        or at least 50 wt. %, or at least 55 wt. %, or at least 55 wt.        %, or at least 60 wt. %, or at least 65 wt. %, or at least 70        wt. %, or at least 75 wt. %, or at least 80 wt. %, and up to 98        wt. %, or up to 95 wt. %, or up to 92 wt. %, or up to 90 wt. %,        or up to 85 wt. %, or up to 80 wt. %, or up to 75 wt. %, or up        to 70 wt. %, or up to 65 wt. %, or up to 60 wt. %, or up to 55        wt. %, or up to 50 wt. %, based on the weight of the sFDCA        composition; and    -   d) FFCA in an amount of at least greater than 0, or at least        0.005 wt. % FFCA, or at least 0.01 wt. % FFCA, or at least 0.05        wt. % FFCA, or at least 0.1 wt. % FFCA, or at least 0.25 wt. %        FFCA, based on the weight of the sFDCA composition. There is not        particular upper limit and the amount can contain 3 wt. % or        less, or up to 2.5 wt. %, or up to 2 wt %, or up to 1.5 wt. %,        based on the weight of the sFDCA composition.

One advantage of the invention is that FDCA solubilizes in water at muchlower temperatures than the temperatures required to dissolveterephthalic acid in water, thereby reducing the energy requirements forobtaining a solution adequate for hydrogenation. Although goodsolubility is also obtained at very high hydrogenation solventtemperatures, it is not necessary to employ such high temperatures toobtain a solution. Thus, the hydrogenation solvent temperature does notneed to exceed 240° C., or 225° C., or 200° C., or even 190° C., or even180° C. to obtain a solvated FDCA solution. The solvated FDCA solutionfed into the hydrogenation reaction zone within the hydrogenationreactor can be at a temperature within the range of 130°-200°, or 135°C.-200° C., or 140° C.-200° C., or 145° C.-200° C., or 150° C.-200° C.,or 130° C.-190° C., or 135° C.-190° C., or 140° C.-190° C., or 145°C.-190° C., or 150° C.-190° C., or 130° C.-185° C., or 135° C.-185° C.,or 140° C.-185° C., or 145° C.-185° C., or 150° C.-185° C., or 130°C.-180° C., or 135° C.-180° C., or 140° C.-180° C., or 145° C.-180° C.,or 150° C.-180° C., or 130° C.-175° C., or 135° C.-175° C., or 140°C.-175° C., or 145° C.-175° C., or 150° C.-175° C.

After providing a sFDCA solution, it is subjected to a hydrogenationreaction in a hydrogenation reaction zone under conditions sufficient tocause hydrogenation of at least a portion of FFCA, and desirably colorbodies. In particular, the sFDCA composition is exposed to hydrogenationconditions in a hydrogenation zone at a temperature within a range of130° C. to 225° C. by contacting the sFDCA composition with hydrogen inthe presence of a hydrogenation catalyst under a hydrogen partialpressure within a range of 10 psi to 900 psi, to thereby produce ahydrogenated furan 2,5-dicarboxylic acid composition (hFDCA) comprisingdissolved FDCA, hydrogenated FFCA, and said hydrogenation solvent. Inthe process of the invention, the cFDCA is purified by catalytichydrogenation of the by-products in the following non-limiting types ofreactions:

As can be seen in the reaction equations above, the intermediate FFCA isconverted to 5-HMFCA, 5-MFCA, FCA and FM, all of which are water solubleand can be separated easily from FDCA through any number of techniques,such as crystallization. In addition, unsaturation in the colored bodiesis converted to saturated species to thereby remove color, and they caneither be removed from the product FDCA or can remain in or on the FDCAproduct.

The sFDCA solution is introduced into a hydrogenation vessel where thesolution is contacted, in the hydrogenation reaction zone, with hydrogenand a hydrogenation catalyst. In the process of the invention,hydrogenation is carried out under mild conditions while effectively anddramatically reducing the amount of FFCA and color bodies. By carryingout hydrogenation under mild conditions, selective hydrogenation can beconducted to minimize hydrogenating the furan ring of the FDCA moleculewhile selectively hydrogenating FFCA and color bodies, compared toconducting hydrogenation under higher temperature and pressure. Further,less energy is consumed to obtain a desired level of intermediatespecies which result in chain termination and to obtain the desiredlevel of color in the final product. A further advantage of carrying outhydrogenation under mild conditions is the diminished risk of degradingthe FDCA molecule.

Hydrogenating the sFDCA solution at a temperature within a range of 130°C. to 225° C., or even less than 200° C., is effective to obtain thedesired level of FFCA and color reduction. The mild hydrogenationtemperature in the hydrogenation reaction zone can be at a temperaturewithin a range of 130° C. -225° C., or 130° C.-205° C., or 130° C.-200°C., or 130° C. to less than 200° C., or 135° C. to less than 200° C., or140° C. to less than 200° C., or 145° C. to less than 200° C., or 150°C. to less than 200° C., or 130°-195°, or 135°-195°, or 140°-195°, or145°-195°, or 150°-195°, or 130° C.-190° C., or 135° C.-190° C., or 140°C.-190° C., or 145° C.-190° C., or 150° C.-190° C., or 130° C.-185° C.,or 135° C.-185° C., or 140° C.-185° C., or 145° C.-185° C., or 150°C.-185° C., or 130° C.-180° C., or 135° C.-180° C., or 140° C.-180° C.,or 145° C.-180° C., or 150° C.-180° C., or 130° C.-175° C., or 135°C.-175° C., or 140° C.-175° C., or 145° C.-175° C., or 150° C.-175° C.The hydrogenation temperature is determined by the temperature of theliquid at or near the liquid discharge port of the hydrogenation reactorin a continuous process or by a thermocouple within the liquid insidethe hydrogenation reactor in a batch process.

The partial pressure of hydrogen in the hydrogenation reaction zonewithin the hydrogenation reactor is also reduced to thereby consume lesshydrogen while maintaining a good reduction of FFCA and color in theresulting product FDCA. The partial pressure of hydrogen in thehydrogenation zone is desirably sufficient to drive at least a portionof the hydrogen into solution. In addition, the partial pressureselected is dependent upon the reaction temperature selected. To avoidhydrogenating the furan ring, the partial pressure of hydrogen should becontrolled at a given reaction temperature. A lower hydrogen partialpressure should be selected if the reaction temperature is at a high,while higher hydrogen partial pressures can be selected if the reactiontemperature is low. The particular values selected within each of thepressure and temperature ranges disclosed above should be effective tolower the b* color and presence of FFCA while minimizing formation ofTHFDCA (the hydrogenated FDCA ring). The partial pressure of hydrogencan vary from from 10 psig to 900 psi, or from 20 psi to 900 psi, orfrom 50 psi to 900 psi, or from 20 psi to 750 psi, or from 50 psi to 750psi, or from 20 psi to 600 psi, or from 50 psi to 600 psi, or from 20psi to 500 psi, or from 50 psi to 500 psi, or from 20 psi to 400 psi, orfrom 50 psi to 400 psi, or from 20 psi to 300 psi, or from 50 psi to 300psi, or from 20 psi to 250 psi, or from 50 psi to 250 psi, or from 20psi to 200 psi, or from 50 psi to 200 psi, or from 20 psi to 150 psi, orfrom 50 psi to 150 psi, or from 20 psi to 100 psi, or from 50 psi to 100psi, or from 20 psi to 90 psi, or from 50 psi to 90 psi. The hydrogenpartial pressure is calculated by subtracting the vapor pressure ofwater or combination of hydrogenation solvents at the reactiontemperature from the total reactor pressure.

The total pressure within the hydrogenation reaction zone is alsodesirably effective to provide a reduction of FFCA and color in theresulting product FDCA without formation of high amounts of THFDCA whilealso sufficient to drive the hydrogen into solution. The total pressurecan vary from 35 psig to less than 950 psig, or from 50 psig to lessthan 950 psig, or from 70 psig to less than 950 psig, or from 35 psig to930 psig, or from 50 psig to 930 psig, or from 70 psig to 930 psig, orfrom 35 psig to 900 psig, or from 50 psig to 900 psig, or from 70 psigto 900 psig, or from 35 psig to 800 psig, or from 50 psig to 800 psig,or from 70 psig to 800 psig, or from 35 psig to 650 psig, or from 50psig to 650 psig, or from 70 psig to 650 psig, or from 35 psig to 550psig, or from 50 psig to 550 psig, or from 70 psig to 550 psig, or from35 psig to 350 psig, or from 50 psig to 350 psig, or from 70 psig to 350psig, or from 35 psig to 300 psig, or from 50 psig to 300 psig, or from70 psig to 300 psig, or from 35 psig to 250 psig, or from 50 psig to 250psig, or from 70 psig to 250 psig, or from 35 psig to 200 psig, or from50 psig to 200 psig, or from 70 psig to 200 psig, or from 35 psig to 150psig, or from 50 psig to 150 psig, or from 70 psig to 150 psig, or from35 psig to 130 psig, or from 50 psig to 130 psig, or from 70 psig to 130psig.

The molar ratio of hydrogen fed to the hydrogenation reaction zone tomoles of FDCA fed to the hydrogenation zone is desirably in the range offrom 0.01:1 to 2:1, or 0.02:1 to 1:1, or from 0.02:1 to less than 1:1,or from 0.02:1 to 0.8:1, or from 0.02:1 to 0.5:1, or from 0.02:1 to0.1:1, or from 0.02:1 to 0.08:1, or from 0.02:1 to 0.06:1.

Hydrogen can be fed into the hydrogenation reaction zone pure at a 100mole % hydrogen concentration or as a mixed feed with other inert gases.The concentration of hydrogen fed into the reaction zone is notparticularly limited. Suitable amounts can be at least 80 wt. %, or atleast 90 wt. %, or at least 95 wt. %, or at least 98 wt. %, or at least99.5 wt. %.

The residence time is effective to reduce the b* color of the sFDCAcomposition and reduce the amount of FFCA while minimizing the formationof THFDCA at the reaction temperature and catalyst type and loadingselected. Examples of suitable residence times of the sFDCA in thehydrogenation reaction zone can range from 15 minutes to 10 hours, and45 minutes to about 5 hours are useful and commercially practical.

The process of the present invention can be operated in a variety ofconfigurations. One such configuration is a fixed bed flow reactionsystem. Desirably, the hydrogenation reaction is conducted in a fixedbed flow reaction system. The substrate to be hydrogenated, the sFDCAsolution, is in the liquid phase in the hydrogenation reaction zone.Another type of suitable configuration is a trickle bed configuration.Regardless of the method of operation, the desired time of contactbetween the sFDCA solution, hydrogen, and catalyst components can bevaried as desired to achieve the desired level of reaction.

The sFDCA solution is contacted with a hydrogenation catalyst in thehydrogenation reaction zone. Any conventional hydrogenation catalyst maybe employed. The hydrogenation catalyst employed in the hydrogenationzone/vessel can be a noble Group VIII metal on a conventional catalystcarrier or support material such as carbon. Although palladium on carbonis a typical hydrogenation catalyst, it is possible to use catalystscontaining other platinum group metals such as ruthenium, rhodium,osmium, iridium and platinum, or an oxide of such a metal or by ametallic catalyst like Pd and/or Rh on carbon. It is also possible touse layered catalyst beds consisting of a layer of Rh on carbon catalystbefore or after the bulk of Pd on carbon catalysts.

The carbon support material can be granular, in pellet form, or anyother particle form. The size of the particles is not limited. The typeof carbon used is also not limited. Activated carbon can be used, and asupport having a surface area of at least 200 m2/gm (measured by the BETMethod) without any upper limit can also be used. A support having asurface area within a range of 200 to 3000 m2/gm is suitable.

The loading of metal onto the support can be from 0.01 wt. % up to 5 wt.%, or from 0.01 to 1.0 wt. %, based on the weight of the final catalystcomposition (including the support). The amount of catalyst metal loadedinto the reaction zone is effective to obtain the desired degree ofconversion without excessive production of THFDCA. The moles of FFCA fedinto the hydrogenation reactor per hour to the moles of total catalystmetal(s) employed can be at least 0.1 hr⁻¹:1, or at least 1 hr⁻¹:1, orat least 5 hr⁻¹:1, or at least 10 hr⁻¹:1, and can be as high as desired.Consideration should be given to the lower limit of the stated ratio toavoid using an excessive amount of total catalyst metal(s) relative tothe moles of FFCA fed that could lead to the formation of excessiveamounts of THFDCA. An excessive amount of catalyst metal can lead tohydrogenation of not only FFCA but also higher amounts of FDCA toconvert FDCA to THFDCA, leading to a yield loss of product. Suitablemolar ratios of FFCA fed per hour to moles of catalyst metal can be upto 150 hr⁻¹:1, or up to 125 hr⁻¹:1, or up to 100 hr⁻¹:1.

The hydrogenation reactor can be any conventional hydrogenation vessel.One example is a hollow cylindrical vessel that horizontally orvertically oriented, desirably is vertically oriented, in which thesFDCA solution is introduced into the hydrogenation reactor at or nearthe top of the vertical vessel or at one end of a horizontal vessel, andin the presence of hydrogen flows down through the reaction chamber orzone and over a fixed catalyst bed supported by mesh, wire, orperforated plates in a vertical vessel or across the catalyst bed in ahorizontally oriented reactor. The hydrogenated FDCA solution isdischarged from the hydrogenation reactor at or near the bottom of thereactor in a vertical reactor or at an end that is distal from the entrypoint in a horizontally oriented reactor. The reactor can be liquid fullor may have a gas head above the liquid level of the sFDCA solution, butthe liquid level should at least submerge the catalyst beds. If notliquid full, the reactor can be operated to maintain a constant liquidlevel by feeding hydrogen gas into the gas space at a rate sufficient tomaintain a constant liquid level. If operated liquid full, the hydrogencan be dissolved in at least a portion of the sFDCA solution with a flowmeter and fed into the hydrogenation reaction zone as a dissolvedhydrogen FDCA solution.

During the hydrogenation process, the following undesired reactions inequations 9, 10, or 11 may occur if the hydrogenation conditions are toosevere, either because the hydrogenation temperature is too high for theresidence time (or average hourly space velocity) employed, or thepartial pressure of hydrogen is too high, or the catalyst loading is toohigh, or a combination of two or more of these activities:

Hydrogenating under conditions that are too severe results inhydrogenating the furan ring, or dissociating a carboxylic acid groupfrom the furan ring, or a combination of both. Thus, it is desirable toconduct the hydrogenation reaction under conditions effective such thatthe hydrogenated FDCA composition (hFDCA) contains no more than 2 wt. %of THFDCA, or no more than 1.5 wt. %, or no more than 1 wt. %, or nomore than 0.8 wt. %, or no more than 0.7 wt. %, or no more than 0.6 wt.%, or no more than 0.5 wt. %, or no more than 0.4 wt. %, or no more than0.3 wt. %, or no more than 0.1 wt. % THFDCA, based on the weight of thehFDCA composition, which includes liquid and solids. While higheramounts of THFDA can be contained within the hFDCA composition, such asless than 10 wt. % THFDCA, or no more than 5 wt. % THFDCA and greaterthan 2 wt. %, based on the weight of the hFDCA composition, such highamount of THFDCA represent a high loss of yield, and a commercialprocess would become impractical to maintain.

Following hydrogenation, the hydrogenated FDCA solution can be recoveredand purified using conventional techniques well known to those of skillin the art. At least a portion of the dissolved FDCA in the hFDCA isconverted to a solid FDCA to thereby produce a product FDCA (pFDCA)composition. For example, at least a portion of the intermediates andcolor bodies which were hydrogenated can be separated from FDCA in thehFDCA solution by any conventional techniques, such as crystallizationto form a crystallized FDCA composition in which at least some of thehydrogenated intermediates (FFCA) and color bodies stay soluble inhydrogenation solvent (e.g. water) and FDCA crystallizes to form FDCAsolids. The FDCA solids can be separated from the crystallized FDCAsolution by solid liquid separation in which the liquids containing atleast a portion of the hydrogenated byproducts (FFCA) and some colorbodies are separated as a mother liquor, optionally followed by washingto wash away any residual mother liquor as a wash waste stream, whichcan be combined with the mother liquor stream if desired.

Instead of or in addition to crystallization, other separationtechniques can be employed for isolating FDCA, such as distillation,solvent/solvent extraction, and the like.

If desired, before crystallization, any carbon particulates separatedfrom the carbon bed and entrained into the hFDCA composition can beseparated from the hFDCA solution by filtration (e.g. pressurefiltration, depth filtration), decantation, and the like.

Desirably, after the optional filtration step to remove carbon bedparticulates from the hydrogenation reactor, the hydrogenated FDCAsolution is crystallized in at least one crystallizer. In thecrystallizer, the temperature of the hydrogenated solution is lowered toa temperature effective to precipitate at least a portion of the FDCA inthe hydrogenated FDCA solution. The crystallization temperature can bein the range of from about 50 to about 200° C., or from about 75 toabout 140° C., or from 50 to 120° C. Desirably, the crystallizationtemperature is at least 20° C. lower, or at least 30° C. lower, or atleast 40° C. lower than the temperature of the hydrogenated FDCAsolution feeding the crystallizer. The crystallization temperature isdesirably above the temperature at which the hydrogenated intermediatesand color bodies would precipitate. If the temperature drop is toosudden and severe, an excessive amount of the hydrogenated intermediatesand color bodies can become encapsulated within the FDCA crystals andthe size of the crystals remain fine. Thus, one may employ multiplecrystallizers in stages that step down the temperature to the desiredend point to increase crystal size and minimize encapsulatingby-products instead of dropping the temperature to the desired end pointin one step.

The decreased temperature in crystallization system causes the majority(more than 50 wt. %, or at least 75 wt. %, or at least 80 wt. %, or atleast 90 wt. %, or at least 95 wt. %, or at least 98 wt. %, or at least99 wt. %) of the FDCA dissolved in the hydrogenated FDCA solution tocrystallize, thereby forming solid particles of a FDCA in a crystallizedFDCA composition. The crystallized FDCA composition contains FDCA solidparticles and in the liquid phase the hydrogenated intermediates andcolor bodies such as 5-HMFCA, 5-MFCA, FCA, FM and other hydrogenatedimpurities remain in solution.

The two-phase crystallized FDCA composition (slurry) discharged from thecrystallizer(s) can thereafter be subjected to solid/liquid separationin a conventional separator, optionally followed by washing with a washsolvent. The separated FDCA solids can be dried in one or moreconventional dryers to produce a product FDCA composition that ispurified. Alternatively, a pFDCA composition can be in the form of a wetcake by avoiding the drying step.

The pFDCA composition desirably has the following composition:

-   -   a) solids, wherein at least 95 wt. %, or at least 97 wt. %, or        at least 98 wt. %, or at least 99 wt. %, or at least 99.5 wt. %,        or at least 99.8 wt. %, or at least 99.9 wt. %, or at least        99.95 wt. % of the solids are FDCA, based on the weight of the        solids;    -   b) a b* of at least zero and less than 4, or less than 3, or        less than 2, or less than 1.5, or less than 1, or less than 0.8,        or less than 0.5;    -   c) FFCA in an amount of less than 500 ppm, or less than 200 ppm,        or less than 100 ppm, or less than 50 ppm, or less than 25 ppm,        or less than 20 ppm, or less than 15 ppm, or no more than 10        ppm;    -   d) and THFDCA present in an amount ranging from zero, or greater        than zero, or at least 1 ppm, or at least 2 ppm, or at least 5        ppm, or at least 10 ppm, or at least 20 ppm, or at least 30 ppm,        or at least 50 ppm, and in an amount of no more than 0.5 wt. %,        or less than 0.4 wt. %, or less than 0.3 wt. %, or less than 0.1        wt. % THFDCA, or less than 500 ppm, or not more than 100 ppm, or        not more than 50 ppm, or not more than 30 ppm, or not more than        25 ppm, or not more than 20 ppm, or not more than 15 ppm, in        each case based on the weight of the solids.

In one embodiment, the pFDCA composition desirably comprises at least 98wt. % solids, or at least 99 wt. % solids, or at least 99.5 wt. %solids, or at least 99.9 wt. % solids, or at least 99.5 wt. % solids.This embodiment would represent an isolated dried solids product.

In another embodiment, the product FDCA composition desirably containsat least 2 wt. % liquid, or at least 4 wt. % liquid, or at least 6 wt. %liquid, and up to 40 wt. % liquid, or up to 30 wt. % liquid, or up to 20wt. % liquid, or up to 15 wt. % liquid, with the remainder solids, andthe solid comprise at least 99 wt. % FDCA and FFC and THFDCA in any ofthe amounts mentioned above. This embodiment would represent a wet cakeproduct.

A very low b* can be obtained in the product FDCA composition byhydrogenating the cFDCA composition. The b* is one of the three-colorattributes measured on a spectroscopic reflectance-based instrument. Thecolor can be measured by any device known in the art. A Hunter UltrascanXE instrument is typically the measuring device. Positive readingssignify the degree of yellow (or absorbance of blue), while negativereadings signify the degree of blue (or absorbance of yellow). Thedescribed and claimed b* values are on the FDCA solids, or a compositioncontaining FDCA solids, that are dissolved into a solution, regardlessof how the sample is initially prepared (e.g. whether or not the samplesare prepared for removal of carbon residuals). All of the b* valuesreported, described or claimed with respect to FDCA (whether a cFDCA,hFDCA, or pFDCA) are based on the solution method of measuring the b* ofthe FDCA solids, and this technique is described with more particularityin the examples.

The process can be operated on a commercial scale. Examples of suitablerates for the production of a pFDCA composition include an average of atleast 1,000 kg/day, or at least 10,000 kg/day, or at least 20,000kg/day, or at least 50,000 kg/day, or at least 75,000 kg/day, or atleast 100,000 kg/day, or at least 200,000 kg/day of a pFDCA compositionon a solids basis, on a 24 hour basis over the course of any threemonths.

The pFDCA composition, which can be either dried carboxylic acid solidsor wet cake, comprising FDCA can be fed to the esterification reactionzone. The pFDCA composition can be shipped via truck, ship, or rail assolids.

The process for making the pFDCA composition can be integrated with theprocess for the manufacture of an esterification facility to make adiester or a polyester. An integrated process includes co-locating thetwo manufacturing facilities, one for hydrogenation, and the other foresterification, within 10 miles, or within 5 miles, or within 2 miles,or within 1 mile, or within ½ mile of each other. An integrated processalso includes having the two manufacturing facilities in solid or fluidcommunication with each other. If a solid dicarboxylic acid compositionis produced, the solids can be conveyed by any suitable means, such asair or belt, to the esterification facility. If a wet cake dicarboxylicacid composition is produced, the wet cake can be moved by belt orpumped as a liquid slurry to the facility for esterification.

The invention has been described in detail with particular reference topreferred embodiments thereof, but will be understood that variationsand modification can be affected within the spirit and scope of theinvention.

Examples 1-12

In Examples 1-12 a 300 mL titanium autoclave equipped with a catalystbasket was charged with 45.0 g of crude colored FDCA (starting b* shownin Table 1) that contained some FFCA and 450.0 g of water. The catalystbasket was charged with 3 grams of a palladium/carbon catalystcontaining 0.5 wt % palladium in an amount as shown in Table 1. Theautoclave was sealed and heated to the desired temperature whileagitating the mixture. H₂ gas was introduced to attain the varioushydrogen partial pressures listed in Table 1. The total pressure wasmaintained from a surge tank during the reaction. The reaction continuedfor the period of time stated in Table 1, upon which the gas supply wasstopped and the autoclave was cooled to room temperature to therebycrystallize FDCA and then depressurized. The heterogeneous mixture wasfiltered to isolate the pFDCA. The mass of the mother liquor filtratewas recorded. The pFDCA solid was washed with 100 mL of water threetimes and it was oven dried at 110° C. under vacuum overnight and thenweighed. The washed and dried solid was analyzed by Gas Chromatographyusing BSTFA derivatization method, HPLC method and solution CIE colormeasurement method. The mother liquor filtrate, before washing anddrying, was also analyzed but only by Gas Chromatography using BSTFAderivatization method to detect the amount of THFDCA. The analyticaltechniques used are further described below. Table 1 sets forth theresults of mild hydrogenation of crude FDCA along with results fromExample 10 which subjected the crude FDCA to hydrogenation conditionsconducive to the formation of high amounts of THFDCA.

The specific methodology one may employ to detect the amount of THFDCA,FFCA, FDCA, and b* are now described.

Gas Chromatographic Method For FDCA Solid Analysis:

Process samples were analyzed using a Shimadzu gas chromatograph Model2010 (or equivalent) equipped with a split/heated injector (300° C.) anda flame ionization detector (300° C.). A capillary column (60 meter×0.32mm ID) coated with (6% cyanopropylphenyl)-methylpolysiloxane at 1.0 μmfilm thickness (such as DB-1301 or equivalent) was employed. Helium wasused as the carrier gas with an initial column head pressure of 29.5 psiand an initial column flow of 3.93 mL/minute while the carrier gaslinear velocity of 45 cm/second was maintained constant throughout theentire oven temperature program. The column temperature was programmedas follows: The initial oven temperature was set at 80° C. and was heldfor 6 minutes, the oven was ramped up to 150° C. at 4° C./minute and washeld at 150° C. for 0 minute, the oven was ramped up to 240° C. at 10°C./minute and was held at 240° C. for 5 minutes, then the oven wasramped up to 290° C. at 10° C./minute and was held at 290° C. for 17.5minutes (the total run time was 60 mins). 1.0-μl of the prepared samplesolution was injected with a split ratio of 40:1. EZ-Chrom Elitechromatography data system software was used for data acquisition anddata processing. The sample preparation was done by weighing 0.1 g(accurate to 0.1 mg) of sample in a GC vial and adding 200.0 μl ISTDsolution (1% by volume of decane in pyridine) and 1000 μl of BSTFA (N,0-bis(trimethylsilyl)trifluoroacetamide) with 1% TMSCl(trimethylchlorosilane) to the GC vial. The content was heated at 80° C.for 30 minutes to ensure complete derivatization. 1.0-μl of thisprepared sample solution was injected for GC analysis.

Gas Chromatographic Method for Detecting THFDCA (Wt % Method):

Process samples were analyzed using a Shimadzu gas chromatograph Model2010 (or equivalent) equipped with a split/splitless, heated injector(300° C.) and a flame ionization detector (300° C.). A capillary column(60 meter×0.32 mm ID) coated with a proprietary stationary phase(ZB-MultiResidue-1) at 0.5 μm film thickness was employed. Helium wasused as the carrier gas with an initial column head pressure of 11.5 psiand an initial column flow of 1.24 mL/minute while the carrier gaslinear velocity of 19.7 cm/second was maintained constant throughout theentire oven temperature program. The column temperature was programmedas follows: The initial oven temperature was set at 50° C. and was heldfor 20 minutes, the oven was ramped up to 280° C. at 10° C./minute andwas held at 280° C. for 17 minute (the total run time was 60 mins).1.0-μl of the prepared sample solution was injected with a split ratioof 60:1. EZ-Chrom Elite chromatography data system software was used fordata acquisition and data processing. The sample preparation was done byweighing 0.0280-0.0300 g (accurate to 0.1 mg) of sample in a GC vial andadding 200.0 μl ISTD solution (1% by volume of decane in pyridine) and1000 μl of BSTFA (N,O-bis(trimethylsilyl)trifluoroacetamide) with 1%TMSCl (trimethylchlorosilane) to the GC vial. The content was heated at80° C. for 45 minutes to ensure complete derivitization. 1.0-μl of thisprepared sample solution was injected for GC analysis.

Gas Chromatographic Method for Detecting THFDCA (Ppm Method):

Process samples were analyzed using a Shimadzu gas chromatograph Model2010 (or equivalent) equipped with a split/splitless, heated injector(300° C.) and a flame ionization detector (300° C.). A capillary column(60 meter×0.32 mm ID) coated with a proprietary stationary phase(ZB-MultiResidue-1) at 0.5 μm film thickness was employed. Helium wasused as the carrier gas with an initial column head pressure of 11.5 psiand an initial column flow of 1.24 mL/minute while the carrier gaslinear velocity of 19.7 cm/second was maintained constant throughout theentire oven temperature program. The column temperature was programmedas follows: The initial oven temperature was set at 50° C. and was heldfor 5 minutes, the oven was ramped up to 280° C. at 10° C./minute andwas held at 280° C. for 32 minute (the total run time was 60 mins).1.0-μl of the prepared sample solution was injected splitless. EZ-ChromElite chromatography data system software was used for data acquisitionand data processing. The sample preparation was done by weighing0.0280-0.0300 g (accurate to 0.1 mg) of sample in a GC vial and adding200.0 μl ISTD solution (1% by volume of decane in pyridine) and 1000 μlof BSTFA (N,O-bis(trimethylsilyl)trifluoroacetamide) with 1% TMSCl(trimethylchlorosilane) to the GC vial. The content was heated at 80° C.for 45 minutes to ensure complete derivitization. 1.0-μl of thisprepared sample solution was injected for GC analysis.

Liquid Chromatographic Method for Low Levels of FFCA in FDCA:

Samples were analyzed with an Agilent 1200 LC unit consisting of aquaternary pump, an autosampler (3 uL injection), a thermostated columncompartment (35C) and a diode array UV/vis detector (280 nm). Thechromatograph was fitted with a 150 mm×4.6 mm Thermo Aquasil C18 columnpacked with 5 micron particles. The solvent flow program is shown in thetable below: Channel A was 0.1% phosphoric acid in water, channel B wasacetonitrile, and channel C was tetrahydrofuran (THF)

Flow Time (min) % A % B % C (ml/min) Initial 95.0 0.0 5.0 1.50 7 95.00.0 5.0 1.50 10 15.0 80.0 5.0 1.50 12 15.0 80.0 5.0 1.50 12.1 95.0 0.05.0 1.50 15 95.0 0.0 5.0 1.50 Equilibration time: 1 minuteEZChrom elite is used for control of the HPLC and for data processing. A5 point linear calibration was used in the (approximate) range of 0.25to 100 ppm FFCA. Samples were prepared by dissolving˜0.05 g (weighedaccurately to 0.0001 g) in 10 ml of 50:50 DMF/THF; higher sample weightsmay be used for samples where the FFCA is present at a very low level,provided that the solubility of FDCA is not exceeded. Sonication wasused to ensure complete dissolution of the sample in the solvent. Aportion of the prepared sample was transferred to an auto sampler vialfor injection onto the LC.

Sample Preparation for b* Measurement

Since hydrogenated FDCA was made in an autoclave without fixing the Pd/Ccatalyst in a bed, and some the carbon particulates became encapsulatedwithin the FDCA solids, to obtain the true b* of the FDCA composition,some of the carbon particulates were first separated. A 10 wt % NH₄OHstock solution was prepared by diluting commercial 30 wt % NH₄OH withwater. 5.0 g of a dry FDCA solid was dissolved in 45.0 g of 10 wt %NH₄OH solution. The mixture was filtered using GHP Acrodisc 25 mmSyringe Filter to remove catalyst carbon particles. The b* of thesolution was measured as discussed below:

Method For Measurement of b*

Samples were analyzed using a Hunter Lab UltraScan Pro spectrophotometerwith an integrating light sphere. Per manufacturer recommendation thespectrophotometer was set to the CIELAB color scale with the D65illuminate and 10° observer. The samples (in this case a 10 wt % NH₄OHstock solution) were transferred to a clear, disposable transmissioncells having a 20 mm path length. The spectrophotometer was standardizedin total transmission mode with a transmission cell filled with 10 wt %NH₄OH stock solution. The purpose of this standardization was tosubtract the background color response of the cell and stock solutionfrom the FDCA sample. The transmission of each sample was then measuredto obtain the CIELAB value for b*.

TABLE 1 crude FDCA solid hydrogen pFDCA solid^(b) % THFDCA FFCA molratio of Temp partial reaction FFCA THFDCA yield in Example (ppmw) b*FFCA to Pd^(a) (° C.) pressure (psi) time (h) (ppmw) (ppmw) b* thefiltrate COMP 1  4000 44.12 15 100 285 3 480 N.M. 36.9 0.05 COMP 2  400044.12 15 120 271 3 260 N.M. 21 0.06 3 10890 53.41 40 150 231 3 <10 770.74 0.65 4 4000 44.12 26 150 231 3 <10 43 0.75 0.64 5 4000 44.12 18 150131 3 <10 36 0.24 0.20 6 19320 61.84 71 170 185 3 <10 18 0.98 0.36 74000 44.12 15 170 135 3 <10 31 0.25 0.11 8 4000 44.12 15 170 85 3 <10 230.34 0.11 9 19320 61.89 71 180 155 3 <10 N.M. 0.96 0.14 COMP 10 1089053.41 40 200 75 3 <10 12 0.24 2.59 11 10890 53.41 40 200 75 1 <10 150.35 <0.03 COMP 12 4000 44.12 15 170 950 3 <10 48 0.4 14.80 ^(a)0.5 wt %Pd on Carbon (CBA −300 SE 11233) was used. ^(b)>99.95% pFDCA purity. N.M= not measured

Comparative Examples 1 and 2 demonstrate that the hydrogenation needs tobe conducted at temperature where FDCA is sufficiently soluble in water.The dissolution temperature should be sufficiently high to obtain gooddissolution of FDCA in the given solvent, otherwise b* and FFCAreduction by hydrogenation will be insufficient.

Examples 3 to 9 and 11 demonstrate that pFDCA with FFCA content of lessthan 10 ppm and a b* of less than 1 can be achieved via mildhydrogenation of crude FDCA.

Comparative Example 10 shows that at elevated hydrogenationtemperatures, excessive ring hydrogenation occurs to form THFDCA in highquantities (appearing in the filtrate). The amount of THFDCA can becontrolled at high hydrogenation temperatures by limiting the residencetime and catalyst loading.

Comparative Example 12 shows that at higher hydrogenation partialpressure, excessive ring hydrogenation occurs to form THFDCA in highquantities (as appearing in the filtrate). The amount of THFDCA can becontrolled at higher hydrogenation partial pressure by limiting theresidence time and catalyst loading.

Comparative Example 13

This example illustrates the effect of severe hydrogenation on an FDCAcomposition. In this example, an large amount of catalyst metal wasemployed and under the hydrogenation conditions (temperature, hydrogenpartial pressure, and residence time), most of the FDCA subjected tohydrogenation was converted to THFDCA.

A 300 mL titanium autoclave equipped with a catalyst basket was chargedwith FDCA (40.0 g, 256 mol) and 450.0 g of water. The catalyst basketwas charged with 13.0 g of palladium/carbon catalyst (40% wet)containing 0.5 wt % palladium. The autoclave was sealed and heated to170° C. while agitating the mixture. H₂ gas was introduced to attain 500psi partial pressure. The total pressure was maintained from the surgetank during the reaction. The reaction continued for 4 h period of timeand gas supply was stopped and the autoclave was cooled to roomtemperature and depressurized. The homogenous aqueous mixture wasfiltered to remove carbon black particles. The water was removed usingrotavap to give a white solid. The white solid was oven dried at 110° C.under vacuum overnight. The product was analyzed by Gas Chromatographyusing BSTFA derivatization method and 91% (38.39 g) of THFDCA wasobtained.

Comparative Example 14

This example illustrates the effect of FDCA hydrogenation under a severereaction temperature.

A 300 mL titanium autoclave equipped with a catalyst basket was chargedwith FDCA (45.0 g, 256 mol) and 450.0 g of water. The catalyst basketwas charged with 3.0 g of palladium/carbon catalyst (40% wet) containing0.5 wt % palladium. The autoclave was sealed and heated to 250° C. whileagitating the mixture. H₂ gas was introduced to attain 135 psi partialpressure. The total pressure was maintained from the surge tank duringthe reaction. The reaction continued for 3 h period of time and gassupply was stopped and the autoclave was cooled to room temperature anddepressurized. The homogenous aqueous mixture was filtered to removecarbon black particles. The water was removed using rotavap to give only2.1 g of intractable sticky solid. Though not bound by the theory mostof FDCA or THFDCA underwent decarboxylation or hydrogenolysis at veryhigh temperature catalyzed by palladium.

What we claim is:
 1. A furan 2,5-dicarboxylic acid compositioncomprising: a) solids, wherein at least 98 wt. % of the solids are FDCA,based on the weight of the solids; b) a b* of less than 4, c) FFCA in anamount of less than 500 ppm; and d) tetrahydrofuran dicarboxylic acid(“THFDCA”) present in an amount ranging from 0 to no more than 0.5 wt.%; in each case based on the weight of the solids.
 2. The composition ofclaim 1, comprising: a) at least 98 wt. % solids; b) a b* of less than 3c) FFCA in an amount of less than 100 ppm; and d) THFDCA in an amount ofless than 100 ppm; in each case based on the weight of the solids. 3.The composition of claim 2, wherein the composition has a b* of not morethan
 1. 4. The composition of claim 1, comprising: a) 99 wt. % solids,wherein at least 99 wt. % of the solids is FDCA; b) a b* of not morethan 1; c) FFCA in an amount of less than 50 ppm; and d) THFDCA in anamount of less than 30 ppm; in each case based on the weight of thesolids.